This invention relates to polycrystalline diamond.
Polycrystalline diamond is the preferred material for the machining of various work pieces, rock drilling applications, and for use as wear parts. The benefits of this material include its superior hardness, diamond being the hardest material known to man, which results in its superior wear resistance. Superior wear resistance in turn imparts various benefits including increased tool or cutter life, less down time, superior work piece finish and performance in application, for example.
Due to the hardness of diamond, it is also brittle. This makes it unsuitable for many applications as it is susceptible to cracking. This inherent brittleness can be significantly reduced by making polycrystalline diamond (PCD), where fine grains of diamond are sintered together to form a polycrystalline structure containing a continuous inter-grown diamond network. In order to achieve diamond intergrowth, a catalysing material, known as a diamond catalyst/solvent, is typically present during synthesis. The catalyst/solvent is typically cobalt, nickel, iron or an alloy containing one or more such metals, preferably nickel and more preferably cobalt. The net result is a continuous diamond skeleton with the catalyst/solvent filling the interstices between the diamond grains. The PCD is generally made under elevated temperature and pressure conditions (HPHT) at which the diamond particles are crystallographically stable.
To further reduce brittleness, this polycrystalline diamond structure may be mounted onto a hardmetal substrate to form a polycrystalline diamond compact, thereby providing a platform behind the PCD, placing it under compression and significantly reducing failure due to brittleness. Hardmetal backed PCD tools offer significant machining and rock drilling benefits and are used extensively.
However, PCD tools are still too brittle for many applications.